1. Field
Embodiments of the invention relates to axial magnetic flux electric rotating machines such as motors and generators, and more particularly to such machines in which flux line penetration between stators and rotors is made more effective than in conventional machines.
2. Description of the Related Art
As described in U.S. Pat. No. 2,469,808, development of axial magnetic flux electrical rotating machines started with a stator core with a pancake design. The inefficient design was changed as described in U.S. Pat. 4,394,597 (hereinafter the '597 Patent). The core configuration taught in the '597 Patent is shown in FIG. 1. The newly designed core could be used either as a stator or a rotor. The core of FIG. 1 is featured with a flat annular surface and slotted section into which electrical conductor windings are placed as shown in FIG. 2. The annular flat surface of the rotor has a counterpart flat surface of a stator arranged in such a manner that the two flat surfaces are parallel, forming an air gap through which, magnetic flux line flows between the rotor and the stator. The magnetic energy from the stator to the rotor is stored in the air gap and is proportional to Bg2, where Bg is the magnetic flux density in the gap. Thus the gap must be as small as possible to maximize Bg, as effective Bg decreases with the gap due to leakage flux. However, there is a limit to the smallest gap as the rotor spins while the stator is stationary. Thus a certain amount of the energy stored in the gap is lost, resulting in an energy loss. In addition to the annular core design, the '597 Patent describes the use of an amorphous magnetic alloy as the core material to enhance energy efficiency of the rotating electrical machine. Subsequent development for a better core design is exemplified in U.S. Pat. No. 6,803,694 (hereinafter the '694 Patent). However, the '694 Patent does not provide substantial improvement of the rotating machine efficiency. It is therefore desirable to invent a new core configuration to make the energy transfer between a rotor and a stator more efficient than the conventional configuration of, for example, FIG. 1. Although the efficiency of the electric rotating machines using amorphous metals is higher than that of the machines based on conventional electric steels, amorphous metals are mechanically much harder than electrical steels, resulting in increased difficulty in machining the amorphous metal-based cores. It is an objective of the present invention to improve the machinability of amorphous metal-based stator and rotor cores and simultaneously to make the magnetic flux flow more effective than in conventional cores.